1. Field of the Invention
The present invention relates to a method of lighting the vacuum fluorescent display, in particular to a method of lighting the vacuum fluorescent display that takes measures to overcome the flickering phenomenon that may appear in the tube due to dynamic lighting.
2. Description of Prior Art
The vacuum fluorescent display is now widely used in various fields, for example it is utilized as an instrument and indicator for the motor vehicle.
In this use, the method of so called dynamic lighting method is usually employed to adjust the luminosity of the vacuum fluorescent display, wherein a pulsed voltage with the duty ratio corresponding to the desired luminosity and with a predetermined high repetition frequency is applied to the anode electrode and/or the grid of the display; consequently the display is turned on and off with a high repetition frequency, which is indiscernible by human vision and the display appears as a light source having the desired luminosity without flickering.
However, if the cathode filament of the display is heated by the AC current, the beat caused by the difference between the repetition frequency pulsed voltage and the frequency of the AC current may have a low frequency that is disadvantageously discernible by human vision.
Accordingly, due to a drawback in the conventional method of dynamic lighting, the vacuum fluorescent display flickers, bothering the watcher of the display.